[Flax Examples] Seq2Seq ASR Fine-Tuning Script (#21764)
* from seq2seq speech
* [Flax] Example script for speech seq2seq
* tests and fixes
* make style
* fix: label padding tokens
* fix: label padding tokens over list
* update ln names for Whisper
* try datasets iter loader
* create readme and append results
* style
* make style
* adjust lr
* use pt dataloader
* make fast
* pin gen max len
* finish
* add pt to requirements for test
* fix pt -> torch
* add accelerate
